1. Field of the Invention
The present invention relates to a method for the production of a piston for an internal combustion engine, having a piston base body and a piston ring element. The piston base body has at least a piston skirt, and the piston ring element has at least a piston crown, a circumferential top land, and a circumferential ring belt provided with ring grooves. The piston base body and the piston ring element form a circumferential, closed cooling channel. The present invention furthermore relates to such a piston for an internal combustion engine.
2. The Prior Art
Friction-welded pistons having cooling channels in the piston head that are open toward the bottom and can be closed off by means of a sheet-metal cover are described in German Patent Application No. DE 10 2004 019 012 A1 and International Application No. WO 2007/128265 A1. In this connection, piston base body and piston ring belt each have only one joining surface. In WO 2007/128265 A1, it is proposed that the joining surfaces are not in contact over their complete area before friction welding, in order to reduce the size of the friction-welding bead that is present below the cooling channel after friction welding, in a controlled manner, so that it is easier to remove subsequent to friction welding. German Patent Application No. DE 10 2004 019 012 A1 discloses a piston base body and a piston ring element whose joining surfaces form a cavity, in order to accommodate excess material during friction welding.
However, neither of these two methods is suitable for producing pistons having a closed, circumferential cooling channel, since the typical pair of rolled-in friction-welding beads formed during friction welding projects radially into the cooling channel. These circumferential friction-welding beads take up a lot of space in the cooling channel. Thus, the volume of the cooling channel is excessively reduced, and the flow of the cooling oil in the cooling channel is hindered. In the case of pistons having a comparatively large combustion chamber bowl, the cooling channel can be configured to be so narrow, in the radial direction, that it would not even be able to accommodate the friction-welding beads.